Preferential decoding of emotion from human non-linguistic vocalizations versus speech prosody.

This study used event-related brain potentials (ERPs) to compare the time course of emotion processing from non-linguistic vocalizations versus speech prosody, to test whether vocalizations are treated preferentially by the neurocognitive system. Participants passively listened to vocalizations or pseudo-utterances conveying anger, sadness, or happiness as the EEG was recorded. Simultaneous effects of vocal expression type and emotion were analyzed for three ERP components (N100, P200, late positive component). Emotional vocalizations and speech were differentiated very early (N100) and vocalizations elicited stronger, earlier, and more differentiated P200 responses than speech. At later stages (450-700ms), anger vocalizations evoked a stronger late positivity (LPC) than other vocal expressions, which was similar but delayed for angry speech. Individuals with high trait anxiety exhibited early, heightened sensitivity to vocal emotions (particularly vocalizations). These data provide new neurophysiological evidence that vocalizations, as evolutionarily primitive signals, are accorded precedence over speech-embedded emotions in the human voice.

Time course of the influence of musical expertise on the processing of vocal and musical sounds.

Previous functional magnetic resonance imaging (fMRI) studies have suggested that different cerebral regions preferentially process human voice and music. Yet, little is known on the temporal course of the brain processes that decode the category of sounds and how the expertise in one sound category can impact these processes. To address this question, we recorded the electroencephalogram (EEG) of 15 musicians and 18 non-musicians while they were listening to short musical excerpts (piano and violin) and vocal stimuli (speech and non-linguistic vocalizations). The task of the participants was to detect noise targets embedded within the stream of sounds. Event-related potentials revealed an early differentiation of sound category, within the first 100 ms after the onset of the sound, with mostly increased responses to musical sounds. Importantly, this effect was modulated by the musical background of participants, as musicians were more responsive to music sounds than non-musicians, consistent with the notion that musical training increases sensitivity to music. In late temporal windows, brain responses were enhanced in response to vocal stimuli, but musicians were still more responsive to music. These results shed new light on the temporal course of neural dynamics of auditory processing and reveal how it is impacted by the stimulus category and the expertise of participants.

The effect of compressed speech on the ability of right-hemisphere-damaged patients to use context.

The ability of RHD patients to use context under conditions of increased processing demands was examined. Subjects monitored for words in auditorily presented sentences of three context types-normal, semantically anomalous, and random, at three rates of speech normal, 70% compressed (Experiment 1) and 60% compressed (Experiment 2). Effects of semantics and syntax were found for the RHD and normal groups under the normal rate of speech condition. Using compressed rates of speech, the effect of syntax disappeared, but the effect of semantics remained. Importantly, and contrary to expectations, the RHD group was similar to normals in continuing to demonstrate an effect of semantic context under conditions of increased processing demands. Results are discussed relative to contemporary theories of laterality, based on studies with normals, that suggest that the involvement of the left versus right hemisphere in context use may depend upon the type of contextual information being processed.

Influence of emotion and focus location on prosody in matched statements and questions.

Preliminary data were collected on how emotional qualities of the voice (sad, happy, angry) influence the acoustic underpinnings of neutral sentences varying in location of intra-sentential focus (initial, final, no) and utterance "modality" (statement, question). Short (six syllable) and long (ten syllable) utterances exhibiting varying combinations of emotion, focus, and modality characteristics were analyzed for eight elderly speakers following administration of a controlled elicitation paradigm (story completion) and a speaker evaluation procedure. Duration and fundamental frequency (f0) parameters of recordings were scrutinized for "keyword" vowels within each token and for whole utterances. Results generally re-affirmed past accounts of how duration and f0 are encoded on key content words to mark linguistic focus in affectively neutral statements and questions for English. Acoustic data on three "global" parameters of the stimuli (speech rate, mean f0, f0 range) were also largely supportive of previous descriptions of how happy, sad, angry, and neutral utterances are differentiated in the speech signal. Important interactions between emotional and linguistic properties of the utterances emerged which were predominantly (although not exclusively) tied to the modulation of f0; speakers were notably constrained in conditions which required them to manipulate f0 parameters to express emotional and nonemotional intentions conjointly. Sentence length also had a meaningful impact on some of the measures gathered.

Context use by right-hemisphere-damaged individuals under a compressed speech condition.

The effect of increased processing demands on context use by RHD individuals was examined using a word-monitoring task. Subjects were required to monitor for a target word in sentences that were either normal, semantically anomalous, or both syntactically and semantically anomalous. Stimuli were presented at two rates of speech--normal and compressed to 70% of normal. Contrary to expectations, the RHD group performed similar to normals in demonstrating an effect of context at both rates of speech. Results are discussed relative to recent studies of normal brain functioning that suggest that the involvement of the LH versus the RH in context use depends upon the type of contextual information being processed.

The temporal organization of affective and non-affective speech in patients with right-hemisphere infarcts.

To evaluate the right hemisphere's role in encoding speech prosody, an acoustic investigation of timing characteristics was undertaken in speakers with and without focal right-hemisphere damage (RHD) following cerebrovascular accident. Utterances varying along different prosodic dimensions (emphasis, emotion) were elicited from each speaker using a story completion paradigm, and measures of utterance rate and vowel duration were computed. Results demonstrated parallelism in how RHD and healthy individuals encoded the temporal correlates of emphasis in most experimental conditions. Differences in how RHD speakers employed temporal cues to specify some aspects of prosodic meaning (especially emotional content) were observed and corresponded to a reduction in the perceptibility of prosodic meanings when conveyed by the RHD speakers. Findings indicate that RHD individuals are most disturbed when expressing prosodic representations that vary in a graded (rather than categorical) manner in the speech signal (Blonder, Pickering, Heath et al., 1995; Pell, 1999a).

Fundamental frequency encoding of linguistic and emotional prosody by right hemisphere-damaged speakers.

To illuminate the nature of the right hemisphere's involvement in expressive prosodic functions, a story completion task was administered to matched groups of right hemisphere-damaged (RHD) and nonneurological control subjects. Utterances which simultaneously specified three prosodic distinctions (emphatic stress, sentence modality, emotional tone) were elicited from each subject group and then subjected to acoustic analysis to examine various fundamental frequency (F(0)) attributes of the stimuli. Results indicated that RHD speakers tended to produce F(0) patterns that resembled normal productions in overall shape, but with significantly less F(0) variation. The RHD patients were also less reliable than normal speakers at transmitting emphasis or emotional contrasts when judged from the listener's perspective. Examination of the results across a wide variety of stimulus types pointed to a deficit in successfully implementing continuous aspects of F(0) patterns following right hemisphere insult.

Recognition of prosody following unilateral brain lesion: influence of functional and structural attributes of prosodic contours.

The perception of prosodic distinctions by adults with unilateral right- (RHD) and left-hemisphere (LHD) damage and subjects without brain injury was assessed through six tasks that varied both functional (i.e. linguistic/emotional) and structural (i.e. acoustic) attributes of a common set of base stimuli. Three tasks explored the subjects' ability to perceive local prosodic markers associated with emphatic stress (Focus Perception condition) and three tasks examined the comprehension of emotional-prosodic meanings by the same listeners (Emotion Perception condition). Within each condition, an initial task measured the subjects' ability to recognize each "type" of prosody when all potential acoustic features (but no semantic features) signalled the target response (Baseline). Two additional tasks investigated the extent to which each group's performance on the Baseline task was influenced by duration (D-Neutral) or fundamental frequency (F-Neutral) parameters of the stimuli within each condition. Results revealed that both RHD and LHD patients were impaired, relative to healthy control subjects, in interpreting the emotional meaning of prosodic contours, but that only LHD patients displayed subnormal capacity to perceive linguistic (emphatic) specifications via prosodic cues. The performance of the RHD and LHD patients was also selectively disturbed when certain acoustic properties of the stimuli were manipulated, suggesting that both functional and structural attributes of prosodic patterns may be determinants of prosody lateralization.

Unilateral brain damage, prosodic comprehension deficits, and the acoustic cues to prosody.

Stimuli from two previously presented comprehension tasks of affective and linguistic prosody (Pell & Baum, 1997) were analyzed acoustically and subjected to several discriminant function analyses, following Van Lancker and Sidtis (1992). An analysis of the errors made on these tasks by left-hemisphere-damaged (LHD) and right-hemisphere-damaged (RHD) subjects examined whether each clinical group relied on specific (and potentially different) acoustic features in comprehending prosodic stimuli (Van Lancker & Sidtis, 1992). Analyses also indicated whether the brain-damaged patients tested in Pell and Baum (1997) exhibited perceptual impairments in the processing of intonation. Acoustic analyses of the utterances reaffirmed the importance of F0 cues in signaling affective and linguistic prosody. Analyses of subjects' affective misclassifications did not suggest that LHD and RHD patients were biased by different sets of the acoustic features to prosody in judging their meaning, in contrast to Van Lancker and Sidtis (1992). However, qualitative differences were noted in the ability of LHD and RHD patients to identify linguistic prosody, indicating that LHD subjects may be specifically impaired in decoding linguistically defined categorical features of prosodic patterns.

The ability to perceive and comprehend intonation in linguistic and affective contexts by brain-damaged adults.

Receptive tasks of linguistic and affective prosody were administered to 9 right-hemisphere-damaged (RHD), 10 left-hemisphere-damaged (LHD), and 10 age-matched control (NC) subjects. Two tasks measured subjects' ability to discriminate utterances based solely on prosodic cues, and six tasks required subjects to identify linguistic or affective intonational meanings. Identification tasks manipulated the degree to which the auditory stimuli were structured linguistically, presenting speech-filtered, nonsensical, and semantically well-formed utterances in different tasks. Neither patient group was impaired relative to normals in discriminating prosodic patterns or recognizing affective tone conveyed suprasegmentally, suggesting that neither the LHD nor the RHD patients displayed a receptive disturbance for emotional prosody. The LHD group, however, was differentially impaired on linguistic rather than emotional tasks and performed significantly worse than the NC group on linguistic tasks even when semantic information biased the target response.

The ability of right- and left-hemisphere-damaged individuals to produce and interpret prosodic cues marking phrasal boundaries.

Two experiments were conducted with the purpose of investigating the ability of right- and left-hemisphere-damaged individuals to produce and perceive the acoustic correlates to phrase boundaries. In the production experiment, the utterance pink and black and green was elicited in three different conditions corresponding to different arrangements of colored squares. Acoustic analyses revealed that both left- and right-hemisphere-damaged patients exhibited fewer of the expected acoustic patterns in their productions than did normal control subjects. The reduction in acoustic cues to phrase boundaries in the utterances of both patient groups was perceptually salient to three trained listeners. The perception experiment demonstrated a significant impairment in the ability of both left-hemisphere-damaged and right-hemisphere-damaged individuals to perceive phrasal groupings. Results are discussed in relation to current hypotheses concerning the cerebral lateralization of speech prosody.

On the receptive prosodic loss in Parkinson's disease.

To comprehensively explore how the processing of linguistic and affective prosodic cues is affected by idiopathic Parkinson's disease (PD), a battery of receptive tests was presented to eleven PD patients without intellectual or language impairment and eleven control subjects (NC) matched for age, gender, and educational attainment. Receptive abilities for both low-level (discrimination) and higher-level (identification) prosodic processing were explored; moreover, the identification of prosodic feature was tested at both the lexical level (phonemic stress perception) and over the sentential domain (prosodic pattern identification). The results obtained demonstrated a general reduction in the ability of the PD patients to identify the linguistic- and affective-prosodic meaning of utterances relative to NC subjects, without a concurrent loss in the ability to perceive phonemic stress contrasts or discriminate prosodic patterns. However, the qualitative pattern of the PD and NC groups' performance across the various identification conditions tested was remarkably uniform, indicating that only quantitative differences in comprehension abilities may have characterized the two groups. It is hypothesized that the basal ganglia form part of a functional network dedicated to prosodic processing (Blonder et al., 1989) and that the processes required to map prosodic features onto their communicative representations at the sentence level are rendered less efficient by the degenerative course of PD.